This invention relates to a hermetic rotary compressor and more particularly to a direct suction system of refrigerant gas into the compressor cylinder and to the assembly process of said suction system.
The gas suction into the high side of rotary compressors is accomplished through a suction tube made of metallic material. When operating, such tube is heated both by gas and oil under high pressure and temperature inside the compressor housing and also by conduction through the parts of the compressor assembly which are under high temperature.
This suction tube heating will in turn cause the heating of the suction gas. Effectively, under usual operation, the difference in the suction gas temperature between the portion of the tube outside the housing and the portion of the tube immediately before the compressor cylinder is about 40.degree. C.
This increase in the temperature reduces the gas specific volume and therefore the filling of the cylinder during each suction cycle, thereby causing a decrease in the compressor capacity. This effect is known in the literature as suction super heating loss.
The conventionally known configuration for the suction system for hermetic compressors, and particularly those of the horizontal rolling piston type, is a metal tube connecting the outside of the housing through its front cover to the compressor components through the wall of the sub-bearing and then through a knee shaped hole which is formed in the cylinder to the inner side of the suction volume portion of the compressor. In addition, there is between the front cover of the housing and the wall of the sub-bearing a portion with a widened diameter which houses a screen which is used to prevent foreign particles from entering inside the compressor set components.
In the conventional compressor configuration there is no attempt made to reduce the suction superheating problem. When the screen is placed into the central widened portion of the tube the problem is increased since the heat transfer surface is increased both in length and in diameter. In addition, the gas flowing through the screen acts as an excellent heat exchange means.